Embodiments of the present invention generally relate to integrated circuits. More particularly, embodiments of the invention provide a system and method for electrostatic discharge (ESD) protection with floating and/or biased polysilicon regions. Merely by way of example, embodiments of the invention have been applied to input pins. But it would be recognized that the invention has a much broader range of applicability.
Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across.
Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as a given process and/or device layout often work down to only a certain feature size. An example of such a limit is the input pin ESD protection provided by certain transistors. An effective protection often requires lowering breakdown voltages of these transistors, but reducing the breakdown voltages can be difficult. Conventionally, an ESD implant may be used for adjusting the breakdown voltages, but the ESD implant often increases fabrication complexity with limited effectiveness.
From the above, it is seen that an improved technique for ESD protection is desired.